Black Holes

vicjameson1

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Just because it acts like a black hole in one respect doesn't make it a black hole, surely. We understand what we call a black hole (mass concentrated at a point), and a cloud of plasma it ain't.

My mouth could be thought of as a black hole as it sucks in matter relentlessly and spews out nothing but informationless energy. Needless to say, it isn't a black hole, it just has some characteristics of one. :roll:
 

Melf

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arent black holes really pink?
:confused:
 

vicjameson1

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One would expect a propensity for red-shifting in the Hawking Radiation as it's coming from a vast gravitational source, thus pinking up the hole :lol:
 

OneWingedBird

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Can someone tell me how Hawking radiation gets out of the black hole? I can understand emissions from the 'outside' of the event horizon as things are consumed, but how can radiation get out when it's generated inside the event horizon? I thought nothing could escape that much gravity?
 

rynner2

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BlackRiverFalls said:
Can someone tell me how Hawking radiation gets out of the black hole? I can understand emissions from the 'outside' of the event horizon as things are consumed, but how can radiation get out when it's generated inside the event horizon?
No, Hawking radiation is created just outside the surface of a black hole.

Particles and anti-particles can spring up anywhere, although normally they quickly recombine to maintain the appearance of conservation of mass/energy.

But when a pair are created just at the surface of a black hole, it's possible for one to be captured while the other flies free. It's the escapees that are the Hawking radiation.

I think...!

EDIT: More info here:
http://en.wikipedia.org/wiki/Hawking_radiation
 

vicjameson1

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That's pretty-much spot on rynner, nothing actually escapes from beyond the event-horizon, it just looks that way from a distance. Particles being created from nothing is an odd (counter-intuitive) occurence in itself, and with this happening so close to extreme space-time events odd physical situations result. Ain't Physics fun ;)
 

Rubyait

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Blast hints at black hole birth


Astronomers are poring over images of a distant galaxy for what may be evidence of the birth of a black hole.

On Monday, the US space agency's (Nasa) Swift satellite detected a brief burst of gamma-rays - high energy radiation - originating from deep space.

Within a minute, Swift was homing in on the burst to be followed by dozens of the world's most powerful telescopes.

It could be due to two neutron stars merging or a collision between a neutron star and black hole.

"It's incredibly exciting. It's what we've been waiting for for years," Professor Josh Bloom, of the University of California, US, told the BBC News website.

Worldwide attention

Swift, launched in November 2004, is designed to monitor the sky for fleeting bursts of gamma-rays. When one is picked-up, it has the ability to quickly turn its main telescopes towards it.

This happened on Monday when it detected a burst designated GRB 050509b. Within 53 seconds of the burst, Swift was registering its decaying radiation. The faint X-ray afterglow had faded completely after 200 seconds.

An e-mail alert was dispatched to observers worldwide.

The giant twin 10m Keck telescopes in Hawaii had their scheduled observations interrupted and, within an hour, one was recording an image of the burst region while the other was obtaining spectra of the optical sources in the region.

They were followed by other optical telescopes in Asia, Europe and the US. Radio telescopes in Europe and the Very Large Array in New Mexico were also employed, though as yet no radio waves have been reported.

To the surprise of the astronomers, the brief burst came from the outskirts of an old elliptical galaxy.

"This was remarkable," said Professor Bloom. "It seems to be coming from a fairly old galaxy, a galaxy with no new stars being formed."

"We have never seen a gamma-ray burst (GRB) coming from an old galaxy like this before."

Short duration burst

Astronomers divide GRBs into two types. The long duration type seems to come from the collapse of young massive stars into black holes.

The short duration type - like GRB 050509b - appears to come from the collision of two neutron stars (which also result in black holes) or a collision between a neutron star and a black hole.

Currently, astronomers are scrutinising the outskirts of the elliptical galaxy to see if they can further refine its location. They have found four, possibly five, faint smudges of light in the region but remain unconvinced that they are anything other than chance alignments.

Some scientists believe that the event could have been accompanied by a burst of neutrinos and the team examining the details of GRB 050509b is asking colleagues monitoring neutrinos from the Sun and deep space to check their detectors' records for the time of the event.


http://news.bbc.co.uk/1/hi/sci/tech/4537905.stm
 
A

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It appears that astronomers have not been able to find an optical counterpart to the gamma ray event;

if two neutron stars did collide to make a black hole (of about 5 solar masses maximum) then the optical flash was not anything like as bright as the gamma-ray flash.
 

Mighty_Emperor

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Horizon

Thu 15 Sep, 9:00 pm - 9:50 pm 50mins

Horizon explores Professor Stephen Hawking's most controversial theory and possibly his greatest mistake.

For 30 years the most famous scientist in the world, Stephen Hawking, defended an extraordinary idea, an idea some claimed would undermine the whole of science. It was called the information paradox. It led one opponent to dub Hawking "the most stubborn man in the universe!" But finally a year ago Hawking had to admit that he'd been wrong all along. Now as he nears the end of his extraordinary career Stephen Hawking's scientific legacy is being called into question like never before.

For a year Horizon has been filming behind the scenes with Hawking as he struggles to finish what many think might be his last scientific paper. If he succeeds he may be able to end his career on a high, confirming his status as one of the great figures in physics. But the odds are against him, as his physical health continues to decline.

This is an extraordinary story of one man's defiance of disability and his peers. It is a story that ranges from the beginning of the universe, which Hawking explored, to the intensive care unit of Addenbrookes, where he was taken and was critically ill for three months. On his hospital bed he had an insight which he hopes will form the basis of his latest comeback. [AD,S]

Subtitles Stereo Widescreen

Website: http://www.bbc.co.uk/horizon/
Direct link:
www.bbc.co.uk/sn/tvradio/programmes/hor ... mary.shtml

Summary:

The Hawking Paradox

Has Stephen Hawking been wrong for the last 30 years?

Stephen Hawking is the most famous scientist on the planet. His popular science book 'A Brief History of Time' was a publishing sensation, staying at the top of the bestseller lists longer than any other book in recent history. But behind the public face lies an argument that has been raging for almost 30 years.

Hawking shot to fame in the world of physics when he provided a mathematical proof for the Big Bang theory. This theory showed that the entire universe exploded from a singularity, an infinitely small point with infinite density and infinite gravity. Hawking was able to come to his proof using mathematical techniques that had been developed by Roger Penrose. These techniques were however developed to deal not with the beginning of the Universe but with black holes.

Science had long predicted that if a sufficiently large star collapsed at the end of its life, all the matter left in the star would be crushed into an infinitely small point with infinite gravity and infinite density – a singularity. Hawking realised that the Universe was, in effect, a black hole in reverse.

Instead of matter being crushed into a singularity, the Universe began when a singularity expanded to form everything we see around us today, from stars to planets to people. Hawking realised that to come to a complete understanding of the Universe he would have to unravel the mysteries of the black hole.

Taming the black hole

Hawking and his fellow physicists embarked on an extraordinary intellectual expedition – to tame the black hole. The period from the early 70s to the early 80s became known as the golden age of black hole research. Slowly physicists were coming to understand this most destructive force of nature.

But Hawking realised that there was something missing from the emerging picture. All work on black holes to that point used the physics of the large-scale Universe, the physics of gravity first developed by Newton and then refined by Einstein's theories of general and special relativity.

Hawking realised that to come to a full understanding of black holes, physicists would also have to use the physics of the small-scale Universe; the physics that had been developed to explain the movements of atoms and sub-atomic particles, known as quantum mechanics.

The problem was that no one had ever combined these two areas of physics before. But that didn't deter Hawking. He set about developing a new way to force the physics of quantum mechanics to co-exist with Einstein's relativity within the intense gravity of a black hole.

Hawking radiation

After months of work Hawking came up with a remarkable result. His equations were showing him that something was coming out of the black hole. This was supposed to be impossible. The one thing that everyone thought they knew about black holes was that things went in but nothing, not even light itself, could escape.

But the more Hawking checked, the more he was convinced he was right. He could see radiation coming out of the black hole. Hawking then realised that this radiation (later called Hawking Radiation) would cause the black hole to evaporate and eventually disappear.

Although Hawking's theories about black hole evaporation were revolutionary, they soon came to be widely accepted. But Hawking knew that this work had far more fundamental consequences. In 1976 he published a paper called 'The Breakdown of Predictability in Gravitational Collapse'. In it he argued that it wasn't just the black hole that disappeared. All the information about everything that had ever been inside the black hole disappeared too.

Are there limits to what science can know?

In everyday life we're used to losing information but according to physics this isn't supposed to happen. Physics has it that information is never really lost, it just gets harder to find. Physicists cling on to this idea because it's their link with either the past or the future. If information is lost then science can never know the past or predict the future. There are limits to what science can know.

For many years no one took much notice of Hawking's ideas until a fateful meeting in San Francisco. Hawking presented his ideas to some of the world's leading physicists. In the audience were Gerad t'Hooft and Leonard Susskind, two leading particle physicists. They were shocked. Both realised that Hawking's 'breakdown of predictability' applied not only to black holes but to all processes in physics. According to Susskind, if Hawking's ideas were correct then it would infect all physics, there would no longer be any direct link between cause and effect. Physics would become impotent.

Since that meeting the 'information paradox' has become one of the most fundamental and most difficult problems in physics. Arguments effectively boiled down into two camps. On the one side were Susskind and those who believed that Hawking was wrong: information could not be lost. On the other were Hawking and those who believed that physics would have to be rewritten to take into account the uncertainty about information that Hawking had uncovered.

For 20 years arguments raged. Neither side was willing to admit defeat. Until a paper emerged by a brilliant young Argentinean mathematician known as Juan Maldacena. It claimed to be a rigorous mathematical explanation of what happened to information in black holes. It showed that information was not lost. Hawking, it seemed, was on the losing side. But he was not convinced.

Hawking set to work with a young research student, Christophe Galfard, to try to pick apart the Maldacena paper. They thought they could use the same mathematical techniques employed by Maldacena to prove that information was in fact lost. But after two years they still could not prove their thesis.

Solving the paradox

Then disaster struck. Hawking was taken ill with pneumonia and rushed to hospital. Doctors feared for his life. He was kept in hospital for over three months. But whilst others fussed over his health, Hawking was thinking. Finally, on what many feared might be his death bed, he thought he'd come across what had eluded him for the past 30 years – a solution to the information paradox.

Once again Hawking defied the doctors' dire predictions and was soon back at work, working on a new proof for the information paradox. Then in July 2004, at one of the most prestigious conferences in physics, Hawking made a dramatic announcement. He claimed to have solved the information paradox. But to the surprise of many in the audience he was not at the conference to defend his long held belief that information was lost in black holes, instead he claimed that he could now prove the opposite.

Hawking presented the outline of a proof that he hoped would at last solve the problem that he had posed almost 30 years earlier. But despite the bold claims, some physicists remain unconvinced. Over a year has passed since the conference and he has still not presented a fully worked mathematical proof to back up his ideas.

But Hawking is a stubborn man. If Hawking is going to change his mind on a view he held for almost 30 years then it will be with his own proof, in his own time. In spite of failing health and increasing problems communicating with his colleagues, he is still working on the proof. If he succeeds in completing a proof that convinces his colleagues, he will not only have solved one of the most difficult problems in physics but he will have managed to have produced ground breaking work at the very end of his career. A feat that even his hero Einstein could not accomplish.
 

TinFinger

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so he is in effect saying a black hole is a data recorder?
just as likelythat black holes are giant garbage compacters that turn complex molecules into electrons/protons possibly this is where they come from.
suns make complex black holes break down again perfect symmetry.
equal and opposit reaction

if you think about it since suns make molcules more complex wouldnt that mean eventually everything would end up as complex as it gets??
surly some counter force must be at work(ok so there is decay but gold is alway such)
 

Jerry_B

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If this means that something cannot truly be destroyed in a black hole, but still survives as data, what happens to all that amassed data when the black hole 'switches off'? Doesn't it mean that all of the undestroyed data collected by the black hole over it's lifetime is still there? If so, where does it go once the black hole no longer exists?
 

bazizmaduno

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I think the point of Hawking's announcement is this:

When a black hole 'swallows' matter, it is converted to energy (remember - enery can neither be created nor destroyed - except perhaps fleetingly as part of virtual particle pairs, which constitute the 'background radiation' of the 'quantum vacuum' - think about the 'casimir effect'.

This was the 'Hawking Radiation'

However, the 'information' contained within matter, i.e spin states, quantum states and degrees of entanglement etc., is not destroyed- it becomes some sot of 'legacy', remaining in/on the event horizon.

I think we must try and understand the difference betwen 'data' and 'information' - data has no 'value' unless it is understood, and which then becomes 'information' - which is useful as it can tell us something.

There is some process in/on the event horizon which makes matter's 'information' unintelligible, but still existant - and I think this is colloquially called 'spaghettification'.

My feelings are that the black hole maths stuff is done in a 3d+time dimentional sort of reference, and that string theory/m-theory referenced math stuff uses more (compactified) dimentions - and it is this frame of reference which makes the 'spaghetti'.

I'll drink some more wine and think on this....

Please, dear people, if someone can correct me - do so - I barely get my head round this...

love and peace

Bazizdefinatelyoffhisfaceuno
 

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Black Holes Aren't So Black

Black Holes Aren't So Black

Common wisdom holds that we can never see a black hole because nothing can escape it - not even light. Fortunately, black holes aren't completely black. As gas is pulled into a black hole by its strong gravitational force, the gas heats up and radiates. That radiation can be used to illuminate the black hole and paint its profile.

Within a few years, astronomers believe they will be able to peer close to the horizon of the black hole at the center of the Milky Way. Already, they have spotted light from "hot spots" just outside the black hole. While current technology is not quite ready for the final plunge, Harvard theorists Avery Broderick and Avi Loeb (Harvard-Smithsonian Center for Astrophysics) already have modeled what observers will see when they look into the maw of this monster.

"It will be really remarkable when observers can see all the way to the edge of the Milky Way's central black hole - a hole 10 million miles in diameter that's more than 25,000 light-years away," said Broderick.

All it will take is a cross-continental array of submillimeter telescopes to effectively create a single telescope as large as the Earth. This process, known as interferometry, has already been used to study longer wavelength radio emissions from outer space. By studying shorter wavelength submillimeter emissions, astronomers could get a high-resolution view of the region just outside the black hole.

"The Holy Grail of black hole astronomy is within our grasp," said Broderick. "We could see the shadow that the black hole casts on surrounding material, and determine the size and spin of the black hole itself."

Infrared observations using existing and near-future interferometric instruments also offer the possibility of imaging the core of our Galaxy in incredible detail, with resolutions better than one milli-arcsecond.

"Submillimeter and infrared observations are complementary," said Smithsonian astronomer Lincoln Greenhill of the Center. "We need to use both to tackle the problem of getting high-resolution observations. It's the only way to get a complete picture of the Galactic center."

The black hole at the center of the Milky Way is the best target for interferometric observations because it spans the largest area in the sky of any known black hole. Nevertheless, its angular size of tens of micro-arcseconds poses a major challenge to observers, requiring resolution 10,000 times better than the Hubble Space Telescope provides in visible light.

"When astronomers achieve it, that first image of the black hole's shadow and inner accretion disk will enter textbooks, and will test our current notions on gravity in the regime where spacetime is strongly curved," said Loeb.

"Ultimately, we want to test Einstein's general theory of relativity in the strong field limit - within a strong gravitational field like that of a black hole," said Broderick.

In preparation for that observational leap, Broderick and Loeb created a computer program to simulate the view. Emissions from the Galaxy's central black hole are known to fluctuate, probably due to clumps of material being swallowed. The researchers modeled those clumps of hot gas and predicted the up-close appearance. They also summed the total light from the "hot spots" to simulate low-resolution observations possible with current technology.

New observational results are starting to come out and already are proving consistent with Broderick and Loeb's prediction.

"Observations to date only span a limited time interval," said Loeb. "With routine monitoring, astronomers will be able to collect many examples of flares and start deriving the characteristics of the black hole itself."

http://www.physorg.com/news6924.html

A paper on the hot-spot modeling has been accepted for publication by the Monthly Notices of the Royal Astronomical Society and is available online at http://arxiv.org/abs/astro-ph/0506433

A second paper modeling the accretion disk has been submitted to The Astrophysical Journal Letters and is available online at http://arxiv.org/abs/astro-ph/0508386

A third paper combining the accretion disk with hot spots has been submitted to Monthly Notices of the Royal Astronomical Society and is available online at http://arxiv.org/abs/astro-ph/0509237

Source: Harvard-Smithsonian Center for Astrophysics
 

bazizmaduno

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"It will be really remarkable when observers can see all the way to the edge of the Milky Way's central black hole - a hole 10 million miles in diameter that's more than 25,000 light-years away," said Broderick.
I didn't think you could tell what the diameter of a black hole was - I though it was more appropriate to give its circumference :?:
 

The late Pete Younger

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bazizmaduno said:
"It will be really remarkable when observers can see all the way to the edge of the Milky Way's central black hole - a hole 10 million miles in diameter that's more than 25,000 light-years away," said Broderick.
I didn't think you could tell what the diameter of a black hole was - I though it was more appropriate to give its circumference :?:
If you know the circumference, you know the diametre surely.
 

rynner2

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Ronson8 said:
bazizmaduno said:
"It will be really remarkable when observers can see all the way to the edge of the Milky Way's central black hole - a hole 10 million miles in diameter that's more than 25,000 light-years away," said Broderick.
I didn't think you could tell what the diameter of a black hole was - I though it was more appropriate to give its circumference :?:
If you know the circumference, you know the diametre surely.
Only if you know what pi is! ;)
 

The late Pete Younger

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rynner said:
Ronson8 said:
bazizmaduno said:
"It will be really remarkable when observers can see all the way to the edge of the Milky Way's central black hole - a hole 10 million miles in diameter that's more than 25,000 light-years away," said Broderick.
I didn't think you could tell what the diameter of a black hole was - I though it was more appropriate to give its circumference :?:
If you know the circumference, you know the diametre surely.
Only if you know what pi is! ;)
Here you go...
LINK
 

bazizmaduno

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Something like this...
http://www.astro.uu.nl/~strous/AA/en/antwoorden/zwarte-gaten.html#v379

For an ordinary object with a particular shape there are fixed relationships between the different measures for the size of the object: If, for example, you know the diameter of a ball, then you can easily calculate the radius, the circumference, the surface area, and the volume of that ball. It really doesn't make much difference which measure you use, because you can calculate the other ones from that one.

Because space and time are strongly distorted near a black hole, such relationships do not necessarily hold there. For example, a black hole doesn't have a diameter of which you can measure the length with something like a ruler, because if you pass through the horizon to start using your ruler, then you can never get out again.

When scientists talk about the diameter of a black hole, then they mean the diameter that an ordinary object has (that is not a black hole) with the same circumference or surface area as the horizon of the black hole. In the simplest case, this is the Schwarzschild diameter, which is proportional to the mass of the black hole
 

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[/b]Massive stars can grow near black holes

For the first time, astronomers have shown that large stars can form close to a supermassive black hole, such as the one at the centre of the Milky Way.

Big stars about 50 times as massive as the Sun are known to exist around the Milky Way's black hole, but how they came to be there was uncertain.

"How a black hole interacts with its surrounding galaxy is a really big question," says Tod Lauer, an astronomer at the National Optical Astronomy Observatory in Tucson, Arizona, US, who was involved in previous studies of blue stars around a black hole in the Andromeda galaxy.

"The first guess would be that stars can't form around black holes - gas comes in, but then gets either eaten or blown away," he told New Scientist. If stars can in fact form close in, as the new results indicate, then astronomers will have to rethink the physics of the activity in all galaxy nuclei, Lauer says.

Nurturing environment
One way to explain the presence of the stars is a scenario in which they form relatively far from the black hole - at least 32 light years away, where the black hole’s gravity is less strong. They are then pulled inward, to within about 0.3 light years.

In an alternative scenario, the tremendous gravitational pull of the black hole – which might easily shred a nascent star – is offset by the gravity of a thick disc of gas around the black hole. Any “lump” in the gas would then collapse into a star. To resist the black hole's pull, the mass of the gas in the disc would have to be equivalent to at least 10,000 solar masses.

Using the Chandra X-ray Observatory to observe Sgr A*, the supermassive black hole at the centre of the Milky Way, two astronomers have now shown the second scenario looks like the correct one.

Evidence of absence
If the inward migration model were right, Chandra should be able to detect X-ray evidence for about a million Sun-sized young stars close to the black hole, along with a much smaller number of larger stars. This was not the case.

"The absence of something expected is as important as the presence of something unexpected," says Sergei Nayakshin, at the University of Leicester, UK, who did the research with Rashid Sunyaev at the Max Planck Institute for Physics in Garching, Germany.

Instead of the low-mass stars, earlier infrared observations show about 100 very large young stars close to the black hole.

The reason why smaller stars appear to form relatively far from black holes but apparently only larger ones form close up is not clear. Nayakshin speculates that the radiation and strong winds from the massive stars could result in an environment that prevents little stars growing.

Massive stars tend not to live very long: they rapidly progress to their deaths in supernova explosions. These spray out relatively heavy elements such as oxygen, and this may explain the heavier elements previously observed in discs around black holes.

http://www.newscientistspace.com/article.ns?id=dn8153
 

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Scientists: Black Hole Helps Spawn Stars

Scientists: Black Hole Helps Spawn Stars
By ALICIA CHANG, AP Science Writer
Fri Oct 14, 2:04 AM ET



Astronomers say the mysterious, massive black hole at the center of the Milky Way helped give birth to new stars, challenging earlier theories that black holes are solely destructive forces.

Scientists peering through NASA's Chandra X-ray Observatory found that disks of gas near the black hole actually helped spawn a new generation of stars.

Their observations, announced Thursday, will be published in a future issue of the Monthly Notices of the Royal Astronomical Society.

"Massive black holes are usually known for violence and destruction," said Sergei Nayakshin of the University of Leicester in England, who made the discovery. "So it's remarkable that this black hole helped create new stars, not just destroy them."

Black holes are believed to be the invisible remains of collapsed stars. Their gravitational pull is so powerful not even light can escape.

This Jekyll-and-Hyde nature suggested by the new discovery may help scientists understand the physics of black holes, said Sterl Phinney, a professor of theoretical astrophysics at the California Institute of Technology in Pasadena, who was not part of the study.

Astronomers believe the gravity of the gas disks helped offset the tidal force of the black hole in a tug-of-war that allowed the stars to form.

Scientists have ruled out the possibility that a star cluster formed far away and somehow migrated near the black hole. Some 10,000 low-mass stars formed near the black hole. If there had been a migration, scientists surmised they would have found at least a million such stars.

The Milky Way is a spiral galaxy, a cluster of stars with a black hole in the center and bending arms spreading out from the core. The solar system, containing the Earth and other planets, is on one of the spiral arms.

___

On the Net:

Chandra X-ray Observatory:
http://chandra.harvard.edu

NASA: http://www.nasa.gov
 

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Spinning black hole leaves dent in space-time


Artist impression of the black hole binary system GRO J1655-4. (Rob Hynes 2001)
MIT scientists and colleagues have found a black hole that has chiseled a remarkably stable indentation in the fabric of space and time, like a dimple in one's favorite spot on the sofa.

The finding may help scientists measure a black hole's mass and how it spins, two long-sought measurements, by virtue of the extent of this indentation. Using NASA's Rossi X-ray Timing Explorer, the team saw identical patterns in the X-ray light emitted near the black hole nine years apart, as captured in archived data from 1996 and in a new, unprecedented 550-hour observation from 2005.

Black hole regions are notoriously chaotic, generating light at a range of frequencies. Similarities seen nine years apart imply something very fundamental is producing a pair of observed frequencies, namely the warping of space and time predicted by Einstein but rarely seen in such detail.

Jeroen Homan of the Kavli Institute for Astrophysics and Space Research at MIT and colleagues from the University of Michigan, Amsterdam University and MIT are presenting this result this week at the annual meeting of the American Astronomical Society in Washington, D.C.

"The fact that we found the exact same frequency of X-ray oscillations nine years later is likely no coincidence," said Homan. "The black hole is still singing the same tune. The oscillations are created by a groove hammered into space-time by the black hole. This phenomenon has been suspected for a while, but now we have strong evidence to support it."

A black hole forms when a very massive star runs out of fuel. Without the power to support its mass, the star implodes and the core collapses to a point of infinite density. Black holes have a theoretical border called an event horizon. Gravity is so strong within the event horizon that nothing, not even light, can escape its pull. Outside the event horizon, light can still escape.

Homan's team -- which includes Jon Miller of the University of Michigan, Rudy Wijnands of Amsterdam University and Walter Lewin of MIT -- observed a region less than 100 miles from the event horizon of a black hole system called GRO J1655-40. Here, matter can orbit a black hole relatively stably, but occasionally it wobbles at certain precise frequencies. This is a direct result of how the black hole deforms space and time, a four-dimensional concept that Einstein called space-time.

The team observed GRO J1655-40 twice a day on average for eight months, for a total of more than 550 hours. Gas from a companion star was falling toward the black hole, heating to high temperatures and causing the entire region to glow in X-ray light.

During the long observation, the team uncovered fluctuations in the X-ray light, called quasi-periodic oscillations, or QPOs. These are thought to be from wobbling blobs of gas whipping around the black hole. The team observed QPOs at frequencies of 300 Hz and 450 Hz -- the same as those observed nine years ago. This was by far the longest observation of a black hole during an outburst. Previous observations have determined that GRO J1655-40 is about 6.5 times more massive than the sun.

"The precise frequencies are determined by the mass of the black hole and also by how fast it spins," said Miller. "Those measurements -- mass and spin -- have been difficult to obtain. Fortunately, we already have an estimate of the mass of this black hole. By understanding the behavior of matter so close to the black hole's edge, we can now begin to determine the spin and thus, for the first time, completely describe the black hole."

Making this detection possible, the team said, was the long and intensive observing program with the Rossi X-ray Timing Explorer, a unique and durable observatory launched on Dec. 30, 1995.

"Had we not observed in this way, we would probably not have detected the pair of QPOs again," said Wijnands. "We need time. X-ray light from black holes typically shows many types of fluctuations. Often we see black holes brighten and weaken a few times per second, but the rate at which this happens changes from day to day. What is so special about the fluctuations that we observed is not only that they are much faster than the ordinary fluctuations -- a few hundred times per second! -- but also that the rate of the fluctuations is exactly the same as when we last saw them, nine years ago."

Source: MIT


http://www.physorg.com/printnews.php?newsid=9731
 

ruffready

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just heard on the radio that there was an explosion in constellation aires

and it should reach earth in a week (to view ) anybody hear about that ? It was just on the radio and I wasn't paying to much attention as I just walked into the room with a handful of cloths to fold. (heard the tail end of it )
 

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ruffready said:
just heard on the radio that there was an explosion in constellation aires

and it should reach earth in a week (to view ) anybody hear about that ? It was just on the radio and I wasn't paying to much attention as I just walked into the room with a handful of cloths to fold. (heard the tail end of it )
This looks like it ruff..possibly a supernova. They've detected the gamma ray burst and it should be getting brighter in the visible spectrum.

http://www.nasa.gov/mission_pages/swift ... burst.html

Scientists Detect New Kind of Cosmic Explosion

02.23.06


Scientists using NASA's Swift satellite have detected a new kind of cosmic explosion. The event appears to be a precursor to a supernova, which is expected to reach peak brightness in one week.

Image above: Scientists are studying a strange explosion that appeared on February 18, 2006, about 440 million light years away in the constellation Aries.

The pinpoint of light from this star explosion outshines the entire host galaxy. Most other sources are foreground stars. Each image is 5 arcminutes by 5 arcminutes. Coordinates for this burst are as follows: RA: 03:21:39.71 Dec: +16:52:02.6 + Click for high res (8.7 Mb) image. Credit: SDSS (left), NASA/Swift/UVOT (right)

Scores of satellites and ground-based telescopes are now trained on the sight, watching and waiting. Amateur astronomers in the northern hemisphere with a good telescope in dark skies can also view it.

The explosion has the trappings of a gamma-ray burst, the most distant and powerful type of explosion known. Yet this explosion, detected on February 18, was about 25 times closer and 100 times longer than the typical gamma-ray burst. And it possesses characteristics never seen before.

"This is totally new and unexpected," said Neil Gehrels, Swift principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md. "This is the type of unscripted event in our nearby universe that we hoped Swift could catch."

The explosion, called GRB 060218 after the date it was discovered, originated in a star-forming galaxy about 440 million light-years away toward the constellation Aries. This is the second-closest gamma-ray burst ever detected, if indeed it is a true burst.

The burst of gamma rays lasted for nearly 2,000 seconds; most bursts last a few milliseconds to tens of seconds. The explosion was surprisingly dim, however, suggesting that scientists might be viewing the event slightly off-axis. Yet this is just one explanation on the table. The standard theory for gamma-ray bursts is that the high-energy light is beamed in our direction.

"There are still many unknowns," said John Nousek, the Swift mission director at Penn State University, State College, Penn. "This could be a new kind of burst, or we might be seeing a gamma-ray burst from an entirely different angle. This off-angle glance --- a profile view, perhaps --- has given us an entirely new approach to studying star explosions. Had this been farther away, we would have missed it."

A team at Italy's National Institute for Astrophysics (INAF) has found hints of a budding supernova. Using the European Southern Observatory's Very Large Telescope in Chile, the scientists have watched the afterglow of this burst grow brighter in optical light. This brightening, along with other telltale spectral characteristics in the light, strongly suggests that a supernova is unfolding.

"We expected to see the typical featureless spectrum of a gamma-ray burst afterglow, but instead we found a mixture between this and the more complex spectrum of a supernova similar to those generally observed weeks after the gamma-ray burst," said Nicola Masetti of INAF's Institute for Space Astrophysics and Cosmic Physics (IASF) in Bologna. "A supernova must be in the works."

Masetti said this could be a Type Ic supernova, characterized by its massive size and the abundance of certain chemical elements. This implies a scenario in which a very massive star has collapsed into a black hole and subsequently exploded; the debris from the explosion is trapping optical light inside and as the dust settles, more and more light will break free.

If they are correct, scientists will have an unprecedented view of a supernova from start to finish across many wavelengths, from radio through X-ray. Radio telescopes in fact have seen this burst from the day it was detected, another first.

Because the burst was so long, Swift was able to observe the bulk of the explosion with all three of its instruments: the Burst Alert Telescope, which detected the burst; and the X-ray Telescope and Ultraviolet/Optical Telescope, which provide high-resolution imagery and spectra across a broad range of wavelengths.

Scientists will attempt observations with the Hubble Space Telescope and Chandra X-ray Observatory. Amateur astronomers in dark skies might be able to see the explosion with a 16-inch telescope as it hits 16th magnitude brightness.

Goddard manges Swift. Swift is a NASA mission with the participation of the Italian Space Agency and the Particle Physics and Astronomy Research Council in the United Kingdom.


Christopher Wanjek
Goddard Space Flight Center
 

ruffready

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Thanks for that! Timble-
The pinpoint of light from this star explosion outshines the entire host galaxy
wow!! thats one big boom!! In Aries mmm. I wonder if other stars near Aries could be affected , like planets around them etc... a wipe out of life on them?? This Universe is really weird!
 

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ruffready said:
In Aries mmm. I wonder if other stars near Aries could be affected , like planets around them etc... a wipe out of life on them?? This Universe is really weird!
Aries is just a constellation, a grouping of stars as seen from Earth - the stars in a constellation are not necessarily close to one another at all. Some of the stars are close to us but relatively faint, while brighter stars may be much more distant.

But yes, a supernova in a nearby star could destroy life on planets on other stars near by.
 

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Right! gotch ya! a star in the direction of aries ( in relation to us looking up at the night sky with a 16 inch reflector would be going Nova! How far away does a star (going super nova ) have to be away from US so as not to be dangerous? Do we have any stars near us that are unstable?
 

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ruffready said:
How far away does a star (going super nova ) have to be away from US so as not to be dangerous? Do we have any stars near us that are unstable?
According to this page..
http://www.universetoday.com/am/publish ... erous.html
.. we're fairly safe, but a GRB could be dangerous at up to 200 ly.

(Nevertheless, I'm keeping my tinfoil hat close at hand! 8) )
 

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Thanks for that rynner!
Are we at risk from GRBs?
Another question still remains: could we be vaporised by a nearby GRB? The answer is no, even though there are GRBs detected almost everyday, scattered randomly throughout the Universe, it is highly unlikely. There are no stars within 200 light years of our Solar System that are of the type destined to explode as a GRB, so we do not expect to witness such an event at close range!
very interesting read. I took astronomy 1 and, astronomy II, in college (way back in '86) my favorite elective!
 

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Three cosmic enigmas, one audacious answer
09 March 2006
Exclusive from New Scientist Print Edition
Zeeya Merali

DARK energy and dark matter, two of the greatest mysteries confronting physicists, may be two sides of the same coin. A new and as yet undiscovered kind of star could explain both phenomena and, in turn, remove black holes from the lexicon of cosmology.

The audacious idea comes from George Chapline, a physicist at Lawrence Livermore National Laboratory in California, and Nobel laureate Robert Laughlin of Stanford University and their colleagues. Last week at the 22nd Pacific Coast Gravity Meeting in Santa Barbara, California, Chapline suggested that the objects that till now have been thought of as black holes could in fact be dead stars that form as a result of an obscure quantum phenomenon. These stars could explain both dark energy and dark matter.

This radical suggestion would get round some fundamental problems posed by the existence of black holes. One such problem arises from the idea that once matter crosses a black hole's event horizon - the point beyond which not even light can escape - it will be destroyed by the space-time "singularity" at the centre of the black hole. Because information about the matter is lost forever, this conflicts with the laws of quantum mechanics, which state that information can never disappear from the universe.

Another problem is that light from an object falling into a black hole is stretched so dramatically by the immense gravity there that observers outside will see time freeze: the object will appear to sit at the event horizon for ever. This freezing of time also violates quantum mechanics. "People have been vaguely uncomfortable about these problems for a while, but they figured they'd get solved someday," says Chapline. "But that hasn't happened and I'm sure when historians look back, they'll wonder why people didn't question these contradictions."

While looking for ways to avoid these physical paradoxes, Chapline and Laughlin found some answers in an unrelated phenomenon: the bizarre behaviour of superconducting crystals as they go through something called "quantum critical phase transition" (New Scientist, 28 January, p 40). During this transition, the spin of the electrons in the crystals is predicted to fluctuate wildly, but this prediction is not borne out by observation. Instead, the fluctuations appear to slow down, and even become still, as if time itself has slowed down.

"That was when we had our epiphany," Chapline says. He and Laughlin realised that if a quantum critical phase transition happened on the surface of a star, it would slow down time and the surface would behave just like a black hole's event horizon. Quantum mechanics would not be violated because in this scenario time would never freeze entirely. "We start with effects actually seen in the lab, which I think gives it more credibility than black holes," says Chapline.

With this idea in mind, they - along with Emil Mottola at the Los Alamos National Laboratory in New Mexico, Pawel Mazur of the University of South Carolina in Columbia and colleagues - analysed the collapse of massive stars in a way that did not allow any violation of quantum mechanics. Sure enough, in place of black holes their analysis predicts a phase transition that creates a thin quantum critical shell. The size of this shell is determined by the star's mass and, crucially, does not contain a space-time singularity. Instead, the shell contains a vacuum, just like the energy-containing vacuum of free space. As the star's mass collapses through the shell, it is converted to energy that contributes to the energy of the vacuum.

The team's calculations show that the vacuum energy inside the shell has a powerful anti-gravity effect, just like the dark energy that appears to be causing the expansion of the universe to accelerate. Chapline has dubbed the objects produced this way "dark energy stars".

Though this anti-gravity effect might be expected to blow the star's shell apart, calculations by Francisco Lobo of the University of Lisbon in Portugal have shown that stable dark energy stars can exist for a number of different models of vacuum energy. What's more, these stable stars would have shells that lie near the region where a black hole's event horizon would form (Classical Quantum Gravity, vol 23, p 1525).

"Dark energy stars and black holes would have identical external geometries, so it will be very difficult to tell them apart," Lobo says. "All observations used as evidence for black holes - their gravitational pull on objects and the formation of accretion discs of matter around them - could also work as evidence for dark energy stars."

That does not mean they are completely indistinguishable. While black holes supposedly swallow anything that gets past the event horizon, quantum critical shells are a two-way street, Chapline says. Matter crossing the shell decays, and the anti-gravity should spit some of the remnants back out again. Also, quark particles crossing the shell should decay by releasing positrons and gamma rays, which would pop out of the surface. This could explain the excess positrons that are seen at the centre of our galaxy, around the region that was hitherto thought to harbour a massive black hole. Conventional models cannot adequately explain these positrons, Chapline says.

He and his colleagues have also calculated the energy spectrum of the released gamma rays. "It is very similar to the spectrum observed in gamma-ray bursts," says Chapline. The team also predicts that matter falling into a dark energy star will heat up the star, causing it to emit infrared radiation. "As telescopes improve over the next decade, we'll be able to search for this light," says Chapline. "This is a theory that should be proved one way or the other in five to ten years."

Black hole expert Marek Abramowicz at Gothenburg University in Sweden agrees that the idea of dark energy stars is worth pursuing. "We really don't have proof that black holes exist," he says. "This is a very interesting alternative."

The most intriguing fallout from this idea has to do with the strength of the vacuum energy inside the dark energy star. This energy is related to the star's size, and for a star as big as our universe the calculated vacuum energy inside its shell matches the value of dark energy seen in the universe today. "It's like we are living inside a giant dark energy star," Chapline says. There is, of course, no explanation yet for how a universe-sized star could come into being.

“The vacuum inside the star has a powerful anti-gravity effect, just like the dark energy that is pulling the universe apart”

At the other end of the size scale, small versions of these stars could explain dark matter. "The big bang would have created zillions of tiny dark energy stars out of the vacuum," says Chapline, who worked on this idea with Mazur. "Our universe is pervaded by dark energy, with tiny dark energy stars peppered across it." These small dark energy stars would behave just like dark matter particles: their gravity would tug on the matter around them, but they would otherwise be invisible.

Abramowicz says we know too little about dark energy and dark matter to judge Chapline and Laughlin's idea, but he is not dismissing it out of hand. "At the very least we can say the idea isn't impossible."
http://www.newscientist.com/channel/fun ... 3.600.html

Fascinating stuff!
 

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"The big bang would have created zillions of tiny dark energy stars out of the vacuum," says Chapline, who worked on this idea with Mazur. "Our universe is pervaded by dark energy, with tiny dark energy stars peppered across it."
advanced aliens could use those as gas stations!

I remember from astronomy any star greater than 8 solar masses when collapsing into itself, will turn into a black hole. Anything under 8 solar masses will become a "white drawf"-I guess they might have to re-write all that in 5 years or so.

that "singularity" at the center of a black hole always got to me..they said you would never reach it, if you went in a black hole, its infinitely small and infinitely dense. :spinning
 
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